Adaptive settings of distance protection to prevent mal-operation under severe voltage fluctuation

A new algorithm for adaptive setting of Zone 3 of distance relays during severe voltage fluctuations is proposed. Conventional relays may mal-operate during under voltage instability condition. The developed algorithm is based on dynamic adjustment of zone 3 setting of distance relays to avoid mal-operation. The proposed algorithm overcomes the pitfall in conventional relays by dynamically changing zone 3 reach setting of the distance relay. The paper describes the new algorithm and presents results obtained from studies on the IEEE 9 bus test system.